Flying the skies

30 March 2013

Last year marked the 70th anniversary of 'atmospheric research flying' — a discipline that, over the years, has helped the Met Office gain a greater understanding of weather systems. But what initially prompted the study of weather from up high?

The story of atmospheric research flights begins in World War II and, specifically, the Battle of Britain. In those relatively early days of flight, much less was known about how a plane interacted with the atmosphere when in flight. The RAF was troubled by aircraft condensation (or vapour) trails as they provided clear indicators of their planes' positions in the sky - making them easier targets for enemy fighters and ground artillery. Discovering the science behind these tell-tale trails became a priority for the RAF - and atmospheric research flying came into being.

Their early airborne investigations found that vapour trails, also known as contrails, were caused by changes in the air pressure as the wing passes though the sky - and were generally more persistent on humid days. Armed with this knowledge, the RAF was able to plan certain flights around weather conditions and therefore minimise the chance of pilots revealing their locations.

"Planes can make unique measurements that can't be made any other way; their research has become one of the most important areas of data collection for the Met Office."

The practice of conducting research in the sky has continued to this day - as Kirsty McBeath, resident Cloud Physics Research Scientist at the Met Office explains:

"Planes can make unique measurements that can't be made any other way; their research has become one of the most important areas of data collection for the Met Office." Such breakthroughs - and the resulting increase in knowledge - made the Met Office realise the value of airborne research. The 'Meteorological Research Flight' (MRF) was formed in 1946, as a follow on to the earlier research done on contrails.

Progress of science

Of course, the measurements made today onboard atmospheric research planes have increased in sophistication - building on many of the breakthroughs made in the early years. The invention of the 'frost-point hygrometer' in 1943 for example, made it possible for scientists to reliably measure humidity in the stratosphere for the first time. This greatly added to scientific knowledge of the lower stratosphere - and enabled researchers to build up a data set on humidity and other elements such as ozone that is still widely used today.

In the early days, data collection from the air was a highly challenging pursuit. With fairly rudimentary equipment, scientists faced a range of conundrums - such as how to measure air temperature while travelling at 300 mph and at an altitude of up to 40,000 ft.

But with every challenge comes the potential for new knowledge and this particular problem was eventually solved by the development of 'thermodynamic theory'. This, in turn, brought about a whole new understanding of the difference between a standard atmosphere and the ones in which pilots fly at various altitudes. And this is still an absolutely essential part of aircraft safety even to this day.

A growing need

Initially, research was conducted on aircraft such as the Mosquito and Flying Fortress. But in the 1950s, the need for data increased - and the size and number of aircraft used followed suit. By the Cold War, specially adapted Canberra aircraft helped the MRF to understand the causes of turbulence. This, in turn, made flying safer and more comfortable for pilots and - as commercial flights became more commonplace - for passengers too.

Later on, the MRF was also involved in backing up and validating data from satellites by providing information about temperature, humidity and clouds. This was yet another undertaking that led to significant improvements in forecasting. Such crucial measurements have only been possible through the development of specially adapted aircraft - a process that was not without challenges, as Kirsty explains:

"Developing instruments for a moving aircraft was not easy. Power supplies were not smooth. Temperatures varied. Flights were often bumpy. Only through experience - alongside a lot of trial and error - did we make any significant headway."

Working together

During the 1970s, international collaboration helped MRF develop further. For example, the MRF team worked with both American and Russian aircraft on the GARP (Global Atmospheric Research Program) Atlantic Tropical Experiment (GATE) - which involved studying convective clouds near the west coast of Africa. This was the largest international meteorological field campaign ever, bringing together 72 different nations including both the USA and Russia - and the results influenced the development of computer models for tropical meteorology.

Another example is a project that ran in collaboration with the Central Electricity Research Laboratory. The project's research on acid rain across Scandinavia led to the implementation of clean air restrictions across Europe - helping to limit the amount of sulphur dioxide and nitrogen oxides above the continent.

In 2001, the MRF, the Natural Environment Research Council (NERC) and the university community joined forces to establish the Facility for Airborne Atmospheric Measurements (FAAM).

The remit of this organisation is to provide an aircraft measurement platform to assist the UK's atmospheric research community on campaigns throughout the world. Most recently they were at the frontline, making in-situ measurements of volcanic ash in the skies over Britain in the days after the 2010 Icelandic volcanic eruption.

Looking back on the historical development of certain scientific disciplines shows how they may be born out of immediate necessity - but also how they can grow and adapt to tackle much more widespread challenges. While atmospheric research flying was prompted by the very acute need to protect the lives of young WWII pilots, today it helps us gain a better understanding of global weather systems and even climate change - a phenomenon that affects us all.

Weather lab in the sky
During the storm that hit Scotland in December 2011, the FAAM research aircraft flew into the eye of the storm using specialist instruments to measure the winds, temperature, humidity and cloud particles.

Watch a video about the Facility for Airborne Atmospheric Measurements (FAAM).